1. Field of the Invention
The invention relates to a rechargeable battery, including a switch, by means of which switch an internal load is connectable to the rechargeable battery, so that the rechargeable battery can be shifted to a predetermined, lower load state.
2. Description of the Prior Art
A rechargeable battery of this kind is already known from German Patent Disclosure DE 10 04 981 A1. Rechargeable lithium-ion cells require a suppressor circuit, which monitors the charging operation and prevents an overly high load state and possible resultant cell damage by blocking further charging. In the rechargeable battery known from DE 101 04 981, ongoing operation should also be monitored, since a load state that is assessed as not yet critical at a low ambient temperature can lead to cell damage at a high temperature. The known rechargeable battery therefore has a relatively complex circuit arrangement, which measures and monitors the load state and the ambient temperature continuously. If the two threshold switches provided for these two parameters respond simultaneously (on reaching a predetermined upper limit value for the temperature on the one hand and for the rechargeable battery voltage—corresponding to a load state—on the other), then the circuit by means of a switch connects a load to the rechargeable battery and discharges the rechargeable battery to such an extent that it is no longer in a critical load state or at a critical temperature.
Lithium rechargeable batteries, however, are problematic, not only in terms of their operation and charging but also in terms of storage of the rechargeable batteries. In general, it must be assumed that accumulators (rechargeable batteries) can be stored equally well not only in the fully or partly charged state but even after all the energy stored in the cells has been completely exhausted. Experience shows, however, that lithium-ion cells especially, and rechargeable batteries constructed of them, on being stored in the (virtually closed) fully charged state are subject to more pronounced aging than is the case for storage in the partially charged or completely discharged state. This aging is expressed in an increase in the internal resistance of the battery and in a irreversible loss of the energy-storing capacity of the lithium-ion batteries.
Storage in the fully charged state, above all, accelerates the aging of the lithium-ion cells, so that even after being stored for a month, a pronounced decrease in the capacity of the rechargeable battery can occur. To avoid this effect, newly manufactured cells are stored and shipped in a partly charged state. If battery packs in use are expected to be stored for a relatively long time, it has been expedient so far not to charge these rechargeable batteries again (fully) after their last use, or by connecting a consumer (a device or an external electrical load) to the lithium-ion rechargeable battery, to shift the rechargeable battery to a partly charged state.